Aspect of light emitting diode (LED) package structures, there already exists a frame type package in which high power light emitting diode dies are put into a base for being packaged, and the packaged high power light emitting diode is further welded onto a aluminum board for basic heat dissipation, and then a heat sink and the high power light emitting diode with the aluminum board are combined. Regarding such frame type package, light emitting diode dies are in advance packaged on a high power base, and the package is arranged to be contacted with the surface of a copper foil through conductive paste and then through a FR4 (epoxy resin fiberglass) aluminum board to dissipate heat by the combination of the conductive paste and the heat dissipation board.
Here, the volume of such frame type package is typically small so that generally a 1˜3 W product is in advance packaged and then put to use in higher wattage products with the arrangement of the aluminum board. In the case of the light board of 7 watts and an aluminum extrusion cylinder of 50 mm*30 mm being used as the heat sink, it is discovered that obvious decline and dim brightness occurred on the light emitting diodes when the temperature of the heat sink is up to 70 degrees Celsius and thus the heat dissipation efficiency decreases.
As to the technique for higher heat dissipation efficiency, in recent years a COB (Chip On Board) package different from the conventional frame type package has been developed, in which more than one LED dies are directly packaged on a aluminum board and then the aluminum board and a heat sink are combined for heat dissipation.
As for such COB package, in the case of the light board of 7 watts and an aluminum extrusion cylinder of 50 mm*30 mm being used as the heat sink, the upper temperature limit is 75 degrees Celsius, but there is still room for improving the heat dissipation efficiency.